1985 game fisher 7.5 over heating

[steamking123]

I have a game fisher 7.5 1985 that I think is over heating. The obvious answer is the impeller is not pumping water. I am pretty sure the impeller is functioning. There is water mist coming out of the exhaust, and water pumps up to the plug at the top of the motor while running.
(see pic)

After running the motor for a few minutes I placed a surface thermometer on the motor (cylinder head) and got several readings ranging from 180 to 200 degrees f.

I have no idea how hot these little motors are suppose to get, but that seems too hot. From my research on this forum, I am pretty sure the cylinder head is air cooled, and the lower unit is what is water cooled.

anyone know what a normal temp reading for a cylinder head is on a small engine?
can the impeller be functioning at half measures?

 

[mrcrabs]

Re: 1985 game fisher 7.5 over heating

pluging that hole might help, check the impeller and run the oil ratio up to say 40:1, its been really hot so your engine will run hotter

 

[steamking123]

Re: 1985 game fisher 7.5 over heating

I already plugged the hole. I just attached the pic to show that the impeller was functioning.

I was running the motor in my garage in a garbage can. It was in the shade less then 90 degree outside.

I don't really want to run the motor on the lake until I know its not over heating. I don't want to burn up the motor.

 

[Tom @ Buzzard Bluff]

Re: 1985 game fisher 7.5 over heating

<I have a game fisher 7.5 1985 that I think is over heating. The obvious answer is the impeller is not pumping water. I am pretty sure the impeller is functioning. There is water mist coming out of the exhaust, and water pumps up to the plug at the top of the motor while running.(see pic)>

From the pic it is obvious that the waterpump is working.

<I am pretty sure the cylinder head is air cooled, and the lower unit is what is water cooled.>

The cylinder and head are air-cooled. It is the lower bearing and seal (the area from which you removed the plug) that must be water-cooled to keep them alive. The cooling of the leg is a secondary benefit of water-cooling the critical lower crankshaft area.

<After running the motor for a few minutes I placed a surface thermometer on the motor (cylinder head) and got several readings ranging from 180 to 200 degrees f. Anyone know what a normal temp reading for a cylinder head is on a small engine? Can the impeller be functioning at half measures?>

I don't own one of the electronic thermometers (tho it's on my list to get if I can ever afford it!) so I can't make an educated comment regarding permissible temperatures of the cylinder head of an air-cooled 2 cycle engine but I strongly suspect that is in the ballpark.
I suggest that you pose the question on a small engine forum for definitive answers. Should you do so please share what you learn with us!

 

[Tom @ Buzzard Bluff]

Addendum

Addendum

To satisfy my own curiosity and try to find some answers for you I pulled my last year model ('86) Eska 7 1/2 model 14209A out of storage today and put it in the tank. It's virtually new and still not well broken in so I was confident that it would be representative of how a late model 7 1/2 in good condition should operate. Took more pulls to crank than normal and then would die after a minute or less---evidence of a carb with some gummed up old gas in it. Since I ALWAYS run them dry before storing I knew that it couldn't have much gum in the carb so I allowed it to sit a while and tried it again with the same result. So I again allowed it to just sit for a while. Next time was the charm---by then the fresh gas had dissolved dried deposits and it lit off and ran cheerfully. This was an object lesson that even tho you 'run her dry' there's always a little left in the bottom of the bowl to cause future problems. It also demonstrates that with a bit of time and patience that they can self-heal if the deposits haven't been there long enough to turn to varnish.

All that aside the impeller I installed in 2006 has little actual running time on it so it pumps like a firetruck. The 2 exhaust relief holes on the back of the leg underneath the lower transom clamp pivot put out a heavy spray of water. It may not appear to the eye as a lot unless the light is just right but putting your hand into it will thoroughly drench it in seconds. And that's what you must do to tell if it's cooling as it should. Even after allowing it to run at a medium idle for 5-10 minutes in neutral I could detect only a little sensible heat in the water . But holding a finger on the cylinder head wasn't feasible unless seeking a good burn! Wish I could be more specific than that but having no means of actual heat measurement the old outboard mechanics method that has worked for almost 100 years at this juncture will have to suffice.

 

[mrcrabs]

Re: 1985 game fisher 7.5 over heating

The cylinder and head are air-cooled. It is the lower bearing and seal (the area from which you removed the plug) that must be water-cooled to keep them alive. The cooling of the leg is a secondary benefit of water-cooling the critical lower crankshaft area.

The water jacket extends to the lower 1/3 of the bottom side of the cylinder.
If you point that thermal temp gun at or near the exhaust port she will be really hot and much cooler back toward the bearing. I ran in the creek yesterday and they do get hot and 180-200 would be no big surprise especially with a hooded engine like the gamefisher. Although you could have a weak seal and or impeller. I would up the mix ratio to 40:1 and take the hood off for hot weather.

 

[Tom @ Buzzard Bluff]

Re: 1985 game fisher 7.5 over heating

It is also worth noting that the fan blades on the flywheel and the fins on cylinder & head must be kept clean to maintain efficiency. The shrouding that directs the air around the finned portion of cylinder and head must be in place and intact as well for the air-cooling system to function as designed.

 

[steamking123]

Re: 1985 game fisher 7.5 over heating

Thanks guys for your help.

Tom- it really helped to have a first hand description of your motor running properly.

At first I didn't think enough water was being pumped through the exhaust to keep it cool. Its hard to see the mist unless you put your hand behind the exhaust port. My experience was similar to yours in that My hand gets drenched after a few seconds.

also its good to know that you would get burned if you touched the cylinder head. the two boat motors that I have worked on have been bigger water cooled engines. I am used to being able to touch the cylinder heads and not get burned. I thought it was overheating because I couldn't touch it. same goes with the pump. My past experience led me to believe that I should be able to easily detect water coming from the exhaust, by just looking at the port.

At this point, I think its actually running normal. I will continue to run at 40:1 and take hood off for hot weather.

 

[Tom @ Buzzard Bluff]

Re: 1985 game fisher 7.5 over heating

Thanks guys for your help.

Tom- it really helped to have a first hand description of your motor running properly.

At first I didn't think enough water was being pumped through the exhaust to keep it cool. Its hard to see the mist unless you put your hand behind the exhaust port. My experience was similar to yours in that My hand gets drenched after a few seconds.

also its good to know that you would get burned if you touched the cylinder head. the two boat motors that I have worked on have been bigger water cooled engines. I am used to being able to touch the cylinder heads and not get burned. I thought it was overheating because I couldn't touch it. same goes with the pump. My past experience led me to believe that I should be able to easily detect water coming from the exhaust, by just looking at the port.

At this point, I think its actually running normal. I will continue to run at 40:1 and take hood off for hot weather.

I'm just glad that it helped you. It was time I gave my motor a bit of exercise anyway as indicated by the gummed carb. I'll check starting and running today if I ever make it to the shop and if still OK I'll 'run her dry', put some preservation treatment in it & return it to the 'ready' rack. I'm now running ONLY pure gas in my pre-mix---NO alcohol---so storage should be less of a risk.

Now put a new impeller in it if you aren't intimately familiar with when it was last renewed.